1. Field of the Invention
This invention broadly relates to methods and apparatus for curing light-curable dental materials such as orthodontic adhesives, dental sealants and dental restorative materials. More particularly, the present invention relates to a portable, small, hand-held curing apparatus that includes at least one solid state light emitter, and methods for using that apparatus.
2. Description of the Related Art
A wide variety of curable materials are used in the field of dentistry. Typical examples include restorative materials (commonly known as xe2x80x9cfillingsxe2x80x9d) and dental sealants. Other examples include various types of dental adhesives such as orthodontic adhesives. Orthodontic adhesives are often used during orthodontic treatment to bond tiny appliances known as brackets to the surfaces of teeth.
Curable dental materials are sometimes supplied as two initially separate components that self-cure once mixed together. Unfortunately, these two-component materials have only a limited xe2x80x9cworking timexe2x80x9d during which the mixture can be placed and manipulated before the mixture begins to harden. As an example, once the components of a two-component orthodontic adhesive are mixed together, the practitioner has only a limited amount of time to transfer the adhesive to the base of the bracket, place the bracket on the tooth and then shift the bracket to a particular desired location on the tooth before the adhesive becomes stiff.
Other dental materials, however, are light-curable and begin to cure only after a source of light is directed toward the material. As can be appreciated, such light-curable materials are widely preferred because the length of the xe2x80x9cworking timexe2x80x9d can be extended as needed. For example, light curable orthodontic adhesives enable the practitioner to take as much time as needed to carefully place the bracket on the patient""s tooth and precisely shift the bracket as desired. Once the practitioner is completely satisfied with the position of the bracket on the tooth, a source of light can then be directed toward the adhesive in order to securely fix the bracket in place.
One type of dental light curing apparatus has a housing with a xe2x80x9cpistol-gripxe2x80x9d configuration. The housing includes a lamp (such as a halogen lamp) that is located in a central section of the housing above the handle. A light guide, often made of a bundle of optical fibers that are fused together, extends outwardly from the housing and is somewhat slender in order to fit within the oral cavity. Typically, the light guide can be swiveled about its longitudinal axis in order to facilitate positioning of the emitted light.
Examples of pistol-grip dental curing apparatus are described, for example, in U.S. Pat. Nos. 4,888,849 and 5,147,204, both of which are assigned to the assignee of the present invention. However, such light curing units are not entirely satisfactory because the housing enclosing the light is somewhat bulky and in some cases obstructs the practitioner""s view of the oral cavity. Unfortunately, it is difficult to reduce the size of the housing because sufficient space must be provided to enclose the lamp as well as an adjacent fan for cooling the lamp during operation.
Recently, there has been increased interest in the use of solid state light emitters to replace the lamps used in dental curing apparatus. Solid state light emitters, such as light emitting diodes (also known as xe2x80x9cLEDsxe2x80x9d) and laser diodes, are typically smaller than the halogen lamps mentioned above. Solid state light emitters also emit less heat than halogen lamps and as a result the need for a fan often can be avoided.
Examples of dental light emitting curing apparatus having solid state light emitters are described in U.S. Pat. Nos. 5,711,665, 5,634,711, 5,487,662 and PCT application No. WO 99/22667. The curing units described in those references are relatively small, compact, light in weight and in some instances operated using a battery. Such construction is an advantage, in that it facilitates maneuvering the apparatus in the oral cavity, a particular benefit in posterior regions of the oral cavity where access is somewhat limited. Additionally, the units are relatively quiet during operation if designed to operate without a fan or other mechanical cooling device.
However, known solid state light emitting dental curing apparatus are not favored in certain applications, because the light emitted from the apparatus has insufficient intensity to adequately cause certain dental materials to cure within a relatively short period of time. To overcome this issue, some have suggested the use of multiple numbers of solid state light emitters positioned closely together in an array. Unfortunately, when multiple solid state light emitters are employed, the power consumption of the apparatus is increased by a corresponding multiple amount, with the result that battery life of the apparatus is reduced. It is possible to increase the size of the battery or to replace the battery with a transformer, rectifier and power cord for connection to a source of A.C. line voltage, but those options hinder maneuverability of the device in use.
High intensity curing units have also been suggested in the past. One example of a commercially available high intensity curing apparatus is known as xe2x80x9cApollo 95Exe2x80x9d from Dental/Medical Diagnostics of Woodland Hills, Calif., and has a xenon bulb that provides plasma arc light. Another example of a high intensity dental light curing apparatus is known as xe2x80x9cLaserMed AccuCure 3000xe2x80x9d from LaserMed of Salt Lake City, Utah, and has an argon laser that emits a blue light.
Conventional high intensity dental curing units, including the high intensity curing apparatus described in the preceding paragraph, are favored by some practitioners because substantially less time is needed to initiate the curing reaction in some light-curable materials. However, such curing units are relatively expensive. Furthermore, the source of light of conventional high intensity dental light curing units is typically located within a base adapted to sit on the practitioner""s countertop or other surface, and a length of light guide such as a glass fiber optic cable or xe2x80x9cliquid cablexe2x80x9d is provided to direct the light where needed. As can be appreciated, the tethered nature of that light guide somewhat restricts maneuverability of the apparatus in use. In addition, many practitioners prefer to avoid dedicating space on the countertop in an area close to the patient""s chair for the base of the unit.
There exists a need in the art for a dental light curing apparatus that can be used with a wide variety of light-curable dental materials, that is highly maneuverable, and yet functions to cure the selected dental material within a relatively short period of time.
The present invention is directed toward a method and apparatus for curing photocurable dental material that involves the use of a solid state light emitter providing greater intensity than known methods and apparatus. In particular, the invention involves overdriving a solid state light emitter to increase the intensity of the emitted light so that the dental material can cure at a faster rate. Although overdriving the solid state light emitter will substantially decrease its life, the apparatus is adapted to be disposable and used with only a single patient. As a result, the expected reduced lifetime of the emitter is not a concern.
In more detail, the invention in one aspect is directed toward a dental light curing apparatus that comprises a housing and a solid state light emitter connected to the housing. The apparatus also includes a source of electrical current connected to the solid state light emitter. A source of electrical current provides a current to the solid state light emitter that is sufficient to reduce the lifetime of the solid state emitter to less than 10 hours.
Another aspect of the invention relates to a method of bonding a quantity of photocurable dental material to a tooth. The method includes the acts of placing a quantity of photocurable material in contact with the tooth and activating a solid state light emitter in order to direct actinic radiation toward the photocurable material. The act of activating a solid state light emitter includes the act of directing an electrical current to the solid state light emitter in an amount sufficient to reduce the lifetime of the solid state light emitter to less than 10 hours.
The invention is also directed to a dental kit that comprises a container and a set of orthodontic brackets received in the container. The kit further includes a solid state light emitter that is received in the container.
The apparatus of the invention provides significant benefits when compared to other known light emitting apparatus for curing dental material. Since the solid state light emitter is overdriven and the apparatus is preferably disposed of after use with a single patient, a battery may be optionally used as a source of power for the apparatus. As such, the apparatus can be self-contained and need not be tethered to an external source of power.
Moreover, use of a solid state light emitter avoids the need for a fan or other cooling mechanism. As a consequence, the apparatus can be relatively inexpensive, compact, light in weight and quiet in operation. The apparatus is highly maneuverable, allowing the light to be directed toward essentially any region of the oral cavity as desired without unduly obstructing the practitioner""s view of the area of interest.